1. Field of the Invention
The present invention relates generally to reinforcing large scale support structures which are present in high moisture environments. More particularly, the present invention involves wrapping a wide variety of structures with composite materials to form reinforcement shells which are specially designed to provide structural reinforcement both in and out of water.
2. Description of Related Art
Concrete columns are widely used as support structures. Bridge supports, freeway overpass supports, building structural supports and parking structure supports are just a few of the many uses for concrete columns. Concrete columns exist in a wide variety of shapes. Concrete columns with circular, square and rectangular cross-sections are most common. However, numerous other cross-sectional shapes have been used including regular polygonal shapes and irregular cross-sections. The size of concrete columns also varies greatly depending upon the intended use. Concrete columns with diameters on the order of 2 to 20 feet and lengths of well over 50 feet are commonly used as bridge or overpass supports.
It is common practice to reinforce concrete columns with metal rods or bars. The metal reinforcement provides a great deal of added structural strength to the concrete column. Although metal reinforcement of concrete columns provides adequate structural reinforcement under most circumstances, there have been numerous incidents of structural failure of metal-reinforced concrete columns when subjected to asymmetric loads generated during earthquakes. The structural failure of a metal reinforced concrete support column during an earthquake can have disastrous consequences. Accordingly, there is a continuing need to enhance the ability of concrete columns to withstand the asymmetric loads which are applied to the column during an earthquake.
One way of increasing the structural integrity of concrete columns is to include additional metal reinforcement prior to pouring the concrete column. Other design features may be incorporated into the concrete column fabrication in order to increase its resistance to asymmetric loading. However, there are hundreds of thousands of existing concrete supports located in earthquake prone areas which do not have adequate metal reinforcement or structural design to withstand high degrees of asymmetric loading. Accordingly, there has been a concentrated effort to develop systems for reinforcing such existing concrete columns to prevent or reduce the likelihood of failure during an earthquake.
One example of a method for increasing the structural strength of existing concrete structures is set forth in U.S. Pat. No. 4,786,341. In this particular patent, the outer surface of the concrete column is reinforced by wrapping a fiber around the column in a variety of different patterns. A problem with this particular method is the amount of time required to wrap a concrete column with a single fiber is time consuming and expensive.
One approach to reinforcing the exterior of an existing concrete support column is set forth in U.S. Pat. No. 5,043,033. In this patent, the exterior of the concrete column is wrapped with a composite material to form a shell surrounding the concrete column. The space between the outer composite shell and the concrete column is then pressurized by injecting a hardenable liquid.
Another approach, as set forth in U.S. Pat. No. 5,218,810 involves wrapping large columns with composite reinforcement layers to form a reinforcing shell which is in direct contact with the column surface.
Although the above reinforcement procedures are well-suited for reinforcing structures in relatively dry environments, they are not suitable for use where water is present. For example, numerous bridge supports columns include substantial portions which are located underwater. Such underwater columns are present in both fresh water and salt water environments. Accordingly, there is a present need to provide composite type reinforcement methods and systems which can be used under water.
In addition to concrete columns, there are numerous other types of structures present in high moisture environments which require periodic reinforcing. Pier or pilings in both fresh water and salt water are made from many different types of materials, including metal, wood and concrete. These types of structures are subject to continual deterioration from the elements. A method and system which can be used simply and efficiently to rehabilitate these types of structures would be extremely advantageous.